1. Field of the Invention
This invention relates to fan assemblies more particularly axial flow fan assemblies. One application of such fan assemblies is in cooling combustion engines such as automobile engines.
2. Description of the Prior Art
U.K. Patent Specification No. 967,100 describes a radial flow fan located in a casing which comprises an outer, gas-tight, wall of a flexible material, an inner, perforated wall of a rigid material such as sheet metal with an absorption layer of foamed or expanded plastics disposed therebetween.
The acoustic absorption material is effective to an extent in absorbing sound emitted by the fan and the casing construction could be applied to an axial flow fan. In the case of an axial flow fan a high-frequency sound is generated at the tips of the fan blades and although sound absorption material can, to an extent, absorb such frequencies, it is desirable to make a further reduction in the level of high-frequency sounds emitted from an axial flow fan assembly and that is the object of the present invention.